Polyolefins are commonly modified by reactive extrusion. The modification is often desirable in order to facilitate the blending of the generally incompatible polyolefins with other polymers. Reactive extrusion functionalizes the polyolefins and thus is a method typically employed to overcome their incompatibility issue with other polymers. Most polyolefins, such as polypropylene, upon grafting have desirable functional rheological properties that permit secondary manipulation or formation of a desired end product. However, the rheological properties of polyethylene or polyethylene copolymers generally change to a less desirable state. One characteristic of grafted polyethylene polymers and copolymers is that their melt flow index decreases upon grafting when compared to the polymer in the ungrafted state.